Method for detecting traffic data

ABSTRACT

The invention relates to a method for acquiring traffic situation data in a network of traffic routes which is covered by a cellular mobile radio network comprising a multiplicity of base stations and in which a multiplicity of vehicles is moving which are in each case provided with an operating mobile terminal for the mobile radio network. In this method, characteristic patterns of values (called signal transit times in the text which follows), which are representative of the signal transit times with respect to the respective base station during the movement of a terminal along the course of the respective traffic route, are determined and permanently stored at least for some of the individual traffic routes of the network of traffic routes at least for selected base stations, the respective characteristic pattern or a sequence of values representative of this pattern is mapped onto the course of the respective traffic route (calibration). To obtain current traffic situation information, the signal transit times of selected terminals which are located within the transmission area of the respective base station are detected and compared with the stored patterns.

PRIORITY CLAIM

This is a U.S. national stage of application Ser. No. PCT/DE01/02217,filed on Jun. 13, 2001. Priority is claimed on that application and onthe following application(s): Country: Germany, Application No.: 100 29115.5, Filed: Jun. 14, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for acquiring traffic situation datain a network of traffic routes which is covered by a cellular mobileradio network comprising a multiplicity of base stations and in which amultiplicity of vehicles is moving which are in each case provided withan operating mobile terminal for the mobile radio network, particularlya mobile telephone, in which method information about signal transittimes between the terminals at the base stations is acquired and usedfor estimating the current location of individual terminals.

2. Description of the Prior Art

Numerous methods for acquiring traffic situation data are known in whichthese data are picked up by vehicles, which participate in the roadtraffic as a fleet of sample vehicles, and are reported to a centralstation by means of mobile radio, specifying the current vehicleposition. The data transmitted to the central station usually containinformation on the position of the vehicle and its speed. The currentvehicle position is determined in the vehicle itself by using, forexample, a satellite navigation system (e.g. GPS). Since a reliabledetection of the traffic situation requires a large number of vehiclesof the fleet of sample vehicles, the data traffic between the vehiclesand the central station results in considerable expenditure. To limitthis expenditure, it is known, for example from EP 0 715 285 B1, toprovide the vehicles of the fleet of sample vehicles, from the centralstation, with advance information about the conditions under which adata transmission from the vehicles to the central station is to beundertaken so that the data traffic can be largely restricted to thecases of disturbances of the traffic flow.

Nevertheless, this method entails not only considerable loading on thechannels of the mobile radio network used but, moreover, also requiresspecial equipment in the individual vehicles of the fleet of samplevehicles.

From DE 198 36 778 A1 , a method is known for locating mobile telephonesin a mobile radio network by triangulation on the basis of signaltransit times between the mobile telephone and a number of base stationswithin the transmitting area of which the mobile telephone is located.In so-called TDMA mobile radio systems, the transit time of each radiolink between the mobile terminal and the base stations of the mobileradio network is determined for the purpose of aligning the terminalsynchronization, that is to say the phase of the TDMA frame at theterminal. Since the transit time of the signal is representative of thedistance between the terminal and the respective base station, thelocation can be determined very simply, in principle, if the distancesto a number of base stations are known. There is thus a possibility ofdetermining the current geographical position of the respective terminalrelative to the known geographic positions of the base stations. Inprinciple, the locating can therefore also be done without using a GPSsystem but, in general, the accuracy is lower because of the limitedresolution (approx. 500 m). In centers of population, in particular, itwould not be possible to unambiguously correlate a mobile terminal,which is in a vehicle on a road, with this road because of this limitedaccuracy.

In DE 198 36 089 A1, a method for determining dynamic trafficinformation is described in which the base stations of a mobile radionetwork which are set up in a network of traffic routes estimate therespective distance to a mobile terminal by means of the received signalstrength and infer movements of the mobile terminal via the change insignal strength. The resolution of this method is comparatively coarseand therefore less suitable, particularly for traffic networks with ahigh density of traffic routes. However, it is also advantageous in thismethod that no special terminals need to be available in the individualvehicles but the presence of, for example, an operating mobile telephonein the vehicle is sufficient.

A further method for acquiring traffic situation data by means of mobileradio networks is known from DE 196 38 798 A1. In this document, amethod is described in which operating parameters in the mobile radionetwork, e.g. the number of handovers at the boundary between two cellson a road, are selectively evaluated. The evaluated operating parametersrelate to operating sequences and states in the mobile radio network andare correlated with certain traffic conditions in the network of trafficroutes. In an initialization phase, data are collected over a relativelylong time and processed to form “profiles”. In the phase of utilization,the operating parameters of the mobile radio network which are currentlydetected are compared with these profiles and any deviations found whichdo not indicate normal traffic conditions are reported to a trafficcontrol center. The disadvantageous factor in this method is that theresolution during the evaluation of handovers at cell boundaries cannotbe reliably reproduced. In addition, the cell boundaries are naturallyarranged to be stationary and thus do not provide an approach to amethod which would be comparable with an acquisition of trafficsituation data by means of a fleet of sample vehicles. The cellboundaries cannot everywhere be unambiguously mapped onto certain roadsegments so that this known method appears to be meaningfully useableonly within local limits and outside of population centers.

SUMMARY OF THE INVENTION

It is the object of the present invention to develop a method of thetype initially mentioned in such a manner that, in spite of the limitedresolution in the determination of the position of a mobile terminal ina mobile radio network, a very reliable detection of the trafficsituation on certain traffic routes of a network of traffic routes canbe guaranteed without requiring the use of special devices which aredirected to the acquisition of traffic situation data in the vehiclesusing the traffic routes. Furthermore, a system of devices for carryingout this method is to be proposed.

The object is met by a method for acquiring traffic situation data in anetwork of traffic routes covered by a cellular mobile radio networkhaving a plurality of base stations, a plurality of vehicles in thenetwork of traffic routes each having an operating mobile terminal forcommunicating with the mobile radio network, signal transit timeinformation related to signal transit times between the mobile terminalsand the base stations being acquired and used for estimating a locationof the each of the mobile terminals. The method includes determiningpatterns of signal transit times representative of signal transit timesbetween a mobile terminal and the base stations of the mobile network ata plurality of points on the traffic routes in the network of trafficroutes during movement of the mobile terminal along courses of thetraffic routes. The determined patterns of signal transit times for atleast a portion of individual traffic routes of the network of trafficroutes are stored for selected base stations. The determined patternsare then mapped onto a corresponding course of the at least a portion ofthe individual traffic routes. After this calibration, current trafficsituation information may be obtained for assessing the trafficsituation by detecting signal transit times of selected ones of themobile terminals located within a transmission area of a respective basestation, comparing the detected signal transit times with the storedpatterns, and deciding on which traffic route of the mobile cellularnetwork the selected ones of the mobile terminals are currently located.

In the method according to the invention, a calibration phase can bedistinguished from a utilization phase and in the calibration phase, thedatabase for carrying out the actual utilization phase in which thecontinuous acquisition of the traffic situation data takes place iscreated. It is an essential feature of the invention that characteristicpatterns of values, which are representative of the signal transit timeswith respect to the respective base station during the movement of aterminal along the course of the respective traffic route, aredetermined and permanently stored in a data base at least for some ofthe individual traffic routes of the network of traffic routes at leastfor selected base stations of the cellular mobile radio networksuperimposed on the network of traffic routes. These values can bestored in the respective base station or also in an arbitrary centralstation for a number of base stations or jointly all base stations. Inthe text which follows, these values are called signal transit times forsimplicity. It is clear that these are not necessarily genuine timevalues but can also be values which correspond to such time values. Whena terminal is moving along a traffic route, for each arbitrary point, aparticular value of the signal transit time between a terminal and aselected base station of the mobile radio network is obtained which,generally, can be reproduced quite well. In principle, a particularsignal transit time to a selected base station can thus be allocated toeach location on a traffic route. In principle, a characteristic patternof signal transit times to a base station is in each case obtained forthe geometric course of a traffic route. Such characteristic patternsor, as a substitute, also a sequence of values representative of such apattern, are mapped onto the course of the respective traffic route inthe second step of the calibration phase of the method according to theinvention. The data base assembled during the calibration phase thusproduces characteristic patterns of signal transit times for theindividual traffic routes, which patterns are mapped onto the course ofthe respective traffic routes and are thus unambiguously correlated withthese so that they represent “reference routes”, as it were.

In the utilization phase of the method in which the current trafficinformation is to be obtained, the current signal transit times ofselected terminals located in the transmission area of the respectivebase station are compared with the stored patterns. If this results insignificant agreements, it is possible to decide with high reliabilitywhich traffic route the respective terminal is currently on or on whichtraffic route it has just been moved. This decision then supplies thebasis for the required information for the assessment of the trafficsituation. If a terminal is found, the pattern of which at currentsignal transit times corresponds to none of the stored characteristicpatterns, this is a terminal which, for example, is carried by apedestrian away from a traffic route or is traveling on a route whichhas hitherto not been subject to the traffic situation surveillance.

It must also be noted with respect to the signal transit times that eachbase station has an unambiguous identifier so that an unambiguouscorrelation is given by appending this identifier to the respectivevalue of the transit time.

The characteristic patterns determined in the calibration phase can beobtained, for example, by statistical evaluations of a multiplicity ofterminals moving over the traffic routes, which, for example, arelocated in vehicles. If many vehicles are moving over the same route,the signal transit times must result in sequences of values which show avery high degree of agreement. Since each location on a route isassociated with a typical value of the signal transit time to therespective base station, each sequence of values must contain amultiplicity of values which similarly also occur in the sequences ofvalues for terminals which have passed along the same route. If thesignal transit times are detected at certain predetermined timeintervals, the number of values determined for a particular route are,naturally, dependent on the respective speed at which the terminal istraveling along the route. The sequence of values must, therefore, becompressed to a standard speed, or pulled apart, to establishcomparability. Figuratively speaking, this means that a less densesequence of measuring points is available for a high speed of movementof the terminal and a denser one for a low speed. Seen graphically, thetotality of these measuring points (signal transit times) corresponds tothe geographic course of the respective traffic route. In practice,deviations of the actual signal transit time from the signal transittime which corresponds to the actual distance of a measuring site on theroute from the respective base station do not lead to errors in themethod according to the invention since the method does not make use ofthe direct calculation of distances but carries out the comparison ofpatterns described above. This is because deviations on the theoreticalsignal transit times occur, in particular, due to stationary disturbinginfluences which affect the characteristic pattern in the same manner asthe current measurements. This automatically eliminates the effects ofcorresponding distortions of the individual values.

Instead of carrying out statistical evaluation for forming thecharacteristic pattern, it is also possible to determine these patternsby continuous acquisition of the signal transit times measured for anindividual moving terminal which is suitably moving in a test vehiclealong the traffic routes in the respective transmission area of a basestation. In each case, it is thus only necessary to travel along thetraffic routes of interest in the network of traffic routes with anoperating terminal of the mobile radio network and to record the signaltransit times. The advantage of this is that an unambiguous correlationwith the road traveled in each case can even be performed during therecording of the data of the characteristic pattern. Naturally, ifnecessary, corresponding signal transit time values for particularlysensitive points or route sections can also be mapped onto theassociated geographic positions.

Although the simple specification of a distance from a base station doesnot yet define an unambiguous location position, a multiplicity ofcorresponding measurement values of the signal transit time to anindividual base station still generates a characteristic pattern whichis generally typical of an individual, quite particular route. Inspecial cases, in which there are symmetric routes of different roadswith respect to the base station, however, the unambiguousness cannot beguaranteed. However, the accuracy of the method according to theinvention is considerably improved if two or more base stations are usedfor forming the characteristic pattern of the signal transit times.Suitably, directly adjoining base stations are in each case selected forforming the pattern for a particular route. The individual locationpositions along the course of the route, i.e. the respective locationsof the terminal, are in this case allocated pairs of values with acorresponding number of individual values per position in accordancewith the number of base stations taken into consideration. These pairsof values thus represent the coordinates of a system of coordinates witha corresponding number of axes.

The direction in which a terminal is moving along a route can be easilydetected from the order in which the individual “route points” of therespective associated characteristic pattern are passed. With respect tothe assessment of the traffic situation, the fact that the terminals aremoving along a particular route provides at least the information that,in principle, the corresponding route can be traveled in the directionof movement detected. If, in addition, the number of terminals moving ina route section is evaluated, information regarding the traffic densitycan be obtained, particularly if representative historical values areavailable for comparison in this respect. However, a particularly goodinformation content of the traffic situation data which can bedetermined according to the invention can be achieved if, in addition tothe signal transit times of the terminals selected for observation,information about the time of the signal transit times determined isalso acquired and temporarily stored. Since the magnitude of the signaltransit times corresponds to a particular location on the respectiveroute, particularly if they were determined for a number of basestations, the time information items and the correlation of the valuesof the signal transit times with geographic locations (at correspondingdistances from one another) can be used for deriving quantities whichare representative of the speed of movement of the respective terminalalong the associated traffic route. Determining the current speedprovides an informative quantity for assessing the traffic situation.

In principle, the measurement values determined according to theinvention can be evaluated within a base station. However, in anadvantageous development of the invention, a traffic situation centercan also be provided which is responsible for a multiplicity of basestations and to which the information obtained is forwarded. This can bedone suitably in such a manner that the data volume is alreadypreprocessed and condensed in each case in the base stations and thatreporting to the traffic situation center is primarily done only whenanomalies are found in the traffic situation of the sector of thenetwork of traffic routes observed in each case.

If the number of terminals which are currently located in a sector ofthe network of traffic routes is small, a large percentage of theterminals is suitably selected for obtaining information for theassessment of the traffic situation. If, for example, only 10 terminalsare active in such a region, all of them are suitably included in theobservation. If, in contrast, the number of terminals operated in such asector is much greater, a restriction to a small percentage may becompletely adequate. Thus, a restriction to a proportion of 20%, forexample, in the case of 100 terminals in the same region and arestriction to 5% in the case of 1 000 terminals in this region ispossible so that the computing effort is not unnecessarily increased. Inprinciple, therefore, it applies that the greater the number ofterminals in an observed sector of the network of traffic routes, thesmaller the percentage of selected devices is allowed to be.

Should there be a number of operating terminals in a vehicle which ismoving in the observed network of traffic routes and these have beenselected for the observation, this can be easily detected from the factthat the transit time values determined and also the time-of-dayinformation thus detected is the same for these devices. In principle,this simulates a higher traffic density. In an advantageous developmentof the invention, it is provided, therefore, that in the case ofdetecting a number of terminals with the same characteristic pattern ofsignal transit times completely or almost at the same time, only one ofthese terminals is taken into consideration for the evaluation.

The method according to the invention can be advantageously used in aGSM mobile radio network.

The spatial resolution in the determination of the position according tothe method according to the invention can be improved by the fact thatthe smallest measuring unit used as a basis in the determination of thesignal transit times in the respective mobile radio network is reduced.In the GSM standard, this measuring unit is, for example, 3.69 μs. Sincethe signal transit time includes the forward and return path, thiscorresponds to a single distance of about 550 m.

In the method according to the invention, it is less a matter ofprecisely locating an individual mobile radio terminal but rather ofcounting and tracking a sufficient number of terminals which are presentin a spatially limited region (e.g. a road section) and are movingcorrespondingly. A great advantage of the present invention lies in thefact that the required communication costs can be kept extraordinarilylow. This is because the essential evaluations can be carried out in therespective base stations in which the signal transit times must bedetermined in any case for operating the mobile radio network. Thecreation of communication costs can be restricted to the cases in whichthe evaluation in a base station indicates the presence of an a typicaltraffic situation which must be forwarded to the central station.

BRIEF DESCRIPTION OF THE DRAWINGS

The only FIGURE shows the transmission area of three base stationsaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The FIGURE shows in a section three base stations BS1, BS2, BS3 of amobile radio network, the transmission area of which includes a mainroad and a side street, the side street leading into the main road. Theincreasing signal transit times in the respective transmission area ofthe base stations BS1, BS2, BS3 are shown in the form of concentriccircles. The individual circles are designated by the numbers 1 to 5 inascending order while the position of the base station itself has thenumber 0. If the smallest unit for the signal transit time is 3.69 μsfor the GSM standard, this means that the region of the first circlecomprises the locations at which the signal transit time is less than3.69 μs. In the region of the next concentric circle 2, the signaltransit times are in each case within a range of once to twice 3.69 μsetc. The step from one circle to the next larger one thus corresponds toa single distance of about 550 m. A terminal moving in the area of thethree base stations will thus generate a sequence of signal transittimes with respect to the three base stations which corresponds to themovement and which is typical of the traffic route used, i.e. isunambiguous. Each measuring point along the road is associated with aset of values of three individual transit times referred to in each caseone of the three base stations. If a terminal carried along in a vehicleis located, for example, on the main road at the turn-off to the sidestreet, the set of values (5; 4; 5) would be determined for thismeasuring point. This means that the terminal is located in circle 5with respect to base station BS1, in circle 4 with respect to basestation BS2 and in circle 5 with respect to base station BS3. If thenthe vehicle is turning into the side street, the “transit timecoordinate” of the base station 1 first briefly remains at the value 5and then rises progressively. At the same time, the “transit timecoordinate” changes briefly from the value 4 and remains for arelatively long time at the value 5 with respect to base station 2whereas the “transit time coordinate” with respect to base station 3first changes from 5 to 4 and then remains at the value 3 for arelatively long time. in this way, a characteristic pattern of transittimes or values corresponding to the transit times can be correlatedwith the geographic course of the route.

1. A method for acquiring traffic situation data in a network of trafficroutes covered by a cellular mobile radio network having a plurality ofbase stations communicating with operating mobile terminals in aplurality of vehicles moving in the network of traffic routes, saidmethod comprising: (a) a calibration phase comprising the steps of:moving at least one of the mobile terminals along the traffic routes;determining at a plurality of points on the traffic routes duringmovement of the at least one of the mobile terminals along the trafficroutes signal transit times to respective base stations having atransmission area in which the at least one of the mobile terminals iscurrently located, each signal transit time being representative of anelapsed time required for transmission of a wireless signal between theat least one of the mobile terminals and one of the respective basestations in the mobile network, whereby the respective base stationsexhibit reference patterns of signal transit times at the plurality ofpoints along the traffic routes; storing for the respective basestations the reference patterns of signal transit times for the trafficroutes; and mapping the reference patterns of signal transit times forthe traffic routes onto the traffic routes; thereby creating a databaseincluding a reference map between the reference patterns of signaltransit times and the traffic routes; and (b) a utilization phasecomprising the steps of: detecting signal transit times of selected onesof the mobile terminals to respective base stations comparing thedetected signal transit times with the stored reference patterns ofsignal transit times; determining on which traffic route the selectedones of the mobile terminals are currently located using the results ofsaid step of comparing and the reference map; thereby obtaininginformation for assessing the traffic situation.
 2. The method of claims1, wherein said step of determining reference patterns comprisesstatistically evaluating signal transit times for a plurality of mobileterminals moving along the traffic routes.
 3. The method of claim 1,wherein said step of determining reference patterns includescontinuously acquiring signal transit times for a single mobile terminalmoving in a vehicle in the transmission area of at least one of the basestations.
 4. The method of claim 1, wherein said step of determiningreference patterns comprises determining sets of signal transit timeswith respect to a plurality of adjacent base stations, wherein arespective location of the mobile terminal corresponds to a specific setof signal transit times.
 5. The method of claim 4, wherein said step ofdetecting signal transit times for selected ones of the mobile terminalsalso includes identifying a time of the detection of the signal transittime and storing the time of detection with the detected signal transittime.
 6. The method of claim 5, further comprising the step of derivinga speed of movement of a mobile terminal along a traffic route using thedetected signal transit times and the corresponding times of detection.7. The method of claim 1, wherein said step of detecting signal transittimes for selected ones of the mobile terminals also includesidentifying a time of the detection of the signal transit time and saidstep of storing includes storing the time of detection with the detectedsignal transit time.
 8. The method of claim 7, further comprising thestep of deriving a speed of movement of a mobile terminal along atraffic route using the detected signal transit times and thecorresponding times of detection.
 9. The method of claim 1, furthercomprising the step of reporting the current traffic situationinformation to a traffic situation center which covers at least a sectorof the mobile cellular network.
 10. The method of claim 9, wherein saidstep of reporting comprises reporting the current traffic situationinformation to the traffic situation center only when an anomaly isfound in the traffic situation of the at least a sector.
 11. The methodof claim 1, wherein said step of obtaining current traffic situationinformation comprises selecting the selected ones of the mobileterminals for which signal transit times are to be detected in responseto a total number of the mobile terminal currently located in area ofdetection, wherein the selected ones comprise a percentage of the totalnumber of mobile terminals which decreases as the total number of mobileterminals correspondingly increases.
 12. The method of claim 1, furthercomprising determining a total number of mobile terminals in an area ofone of the traffic routes of the network of traffic routes forfacilitating assessment of the traffic situation.
 13. The method ofclaim 1, wherein said step of detecting signal transit times forselected ones of the mobile terminals also includes identifying a timeof the detection of the signal transit time, said method furthercomprising considering only one of a plurality of mobile terminals thatexhibit the same pattern at the same time.
 14. The method of claim 1,wherein the mobile cellular network is a GSM mobile radio network. 15.The method of claim 1, further comprising the step of reducing thesmallest measuring unit in the determination of the signal transit timeto improve spatial resolution.
 16. A system for acquiring trafficsituation data in a network of traffic routes covered by a cellularmobile radio network having a plurality of base stations, a plurality ofvehicles moving in the network of traffic routes, and each of theplurality of vehicles having an operating mobile terminal forcommunicating with the mobile radio network, said system comprising:means for creating a database including means for determining at aplurality of points on the traffic routes during movement of at leastone of the mobile terminals along the traffic routes signal transittimes to respective base stations having a transmission area in whichthe at least one of the mobile terminals is currently located, eachsignal transit time being representative of an elapsed time required fortransmission of a wireless signal between the at least one of the mobileterminals and one of the respective base stations in the mobile network,whereby the respective base stations exhibit reference patterns ofsignal transit times at the plurality of points along the trafficroutes; means for storing for the respective base stations the referencepatterns of signal transit times for the traffic routes; and means formapping the reference patterns of signal transit times for the trafficroutes onto the traffic routes, and for thereby creating the databaseincluding a reference map between the reference patterns of signaltransit times and the traffic routes; and means for using the databaseto assess a traffic situation including means for detecting signaltransit times of selected ones of the mobile terminals to respectivebase stations; means for comparing the detected signal transit timeswith the stored reference patterns of signal transit times; and meansfor determining on which traffic route the selected ones of the mobileterminals are currently located using the results of said means forcomparing and the reference map, and thereby for obtaining informationfor assessing the traffic situation.
 17. The system of claim 16, whereinsaid means for determining reference patterns comprises means forstatistically evaluating signal transit times for a plurality of mobileterminals moving along the traffic routes.
 18. The system of claim 16,wherein said means for determining reference patterns includes means forcontinuously acquiring signal transit times for a single mobile terminalmoving in a vehicle in the transmission area of at least one of the basestations.
 19. The system of claim 16, wherein said means for determiningreference patterns comprises determining sets of signal transit timeswith respect to a plurality of adjacent base stations, wherein arespective location of the mobile terminal corresponds to a specific setof signal transit times.
 20. The system of claim 19, wherein said meansfor detecting signal transit times for selected ones of the mobileterminals also includes means for identifying a time of the detection ofthe signal transit time and said means for storing includes means forstoring the time of detection with the signal transit time.
 21. Thesystem of claim 20, further comprising means for deriving a speed ofmovement of a mobile terminal along a traffic route using the detectedsignal transit times and the corresponding times of detection.
 22. Thesystem of claim 16, wherein said means for detecting signal transittimes for selected ones of the mobile terminals also includes means foridentifying a time of the detection of the signal transit time and saidmeans for storing includes means for storing the time of detection withthe signal transit time.
 23. The system of claim 22, further comprisingmeans for deriving a speed of movement of a mobile terminal along atraffic route using the detected signal transit times and thecorresponding times of detection.
 24. The system of claim 16, furthercomprising means for reporting the current traffic situation informationto a traffic situation center which covers at least a sector of themobile cellular network.
 25. The system of claim 24, wherein said meansfor reporting comprises means for reporting the current trafficsituation information to the traffic situation center only when ananomaly is found in the traffic situation of the at least a sector. 26.The system of claim 16, wherein said means for obtaining current trafficsituation information comprises selecting the selected ones of themobile terminals for which signal transit times are to be detected inresponse to a total number of the mobile terminal currently located inarea of detection, wherein the selected ones comprise a percentage ofthe total number of mobile terminals which decreases as the total numberof mobile terminals correspondingly increases.
 27. The system of claim16, further comprising means for determining a total number of mobileterminals in an area of one of the traffic routes of the network oftraffic routes for facilitating assessment of the traffic situation. 28.The system of claim 16, wherein said means for detecting signal transittimes for selected ones of the mobile terminals also includesidentifying a time of the detection of the signal transit time, saidsystem further comprising means for considering only one of a pluralityof mobile terminals that exhibit the same pattern at the same time. 29.The system of claim 16, wherein the mobile cellular network is a GSMmobile radio network.
 30. The system of claim 16, further comprising thestep of reducing the smallest measuring unit in the determination of thesignal transit time to improve spatial resolution.